From: Ian Jackson <ian.jackson@eu.citrix.com>
Date: Tue, 24 Oct 2017 15:14:41 +0000 (+0100)
Subject: fishdescriptor: wip utility
X-Git-Tag: archive/debian/6.0.0~1^2~17
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=chiark-utils.git;a=commitdiff_plain;h=73e1fb3006255b522bad36c22e9ebb0dd3ba49bb

fishdescriptor: wip utility

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---

diff --git a/fishdescriptor/fishdescriptor b/fishdescriptor/fishdescriptor
index bdddff2..863cf83 100755
--- a/fishdescriptor/fishdescriptor
+++ b/fishdescriptor/fishdescriptor
@@ -7,9 +7,7 @@ import re
 
 donor = None
 
-usage =
-'''
-fishdescriptor [-p|--pid] <pid> <action>... [-p|--pid <pid> <action>...]
+usage = '''fishdescriptor [-p|--pid] <pid> <action>... [-p|--pid <pid> <action>...]
 
 <action>s
   [<here-0fd>=]<there-fd>
@@ -27,22 +25,25 @@ fishdescriptor [-p|--pid] <pid> <action>... [-p|--pid <pid> <action>...]
           now attach to <pid>, detaching from previous pid
 '''
 
+pending = []
+# list of (nominal, there) where nominal might be None
+
 fdmap = { }
-# fdmap[here] = (actual_fd_number_here, Donor, target_fd)
+# fdmap[nominal] = (actual, Donor, there)
 
-last_here = None
+last_nominal = None
 
 def implement_pending():
-    got_list = donor.fish([x[1] for x in pending])
-    assert(len(got_list) = len(pending))
-    for (here, there), got in zip(pending, got_list)
-        overwriting = fdmap.get(here)
-        if overwriting is not None: os.close(overwriting)
-        fdmap[here] = (got, Donor, there)
-        last_here = here
-
-def implmement_sockinfo(here):
-    (fd, tdonor, there) = fdmap[here]
+    actuals = donor.fish([pend[1] for pend in pending])
+    assert(len(actuals) == len(pending))
+    for (nominal, there), actual in zip(pending, actuals)
+        overwriting_info = fdmap.get(nominal)
+        if overwriting_info is not None: os.close(overwriting_info[0])
+        fdmap[nominal] = (actual, Donor, there)
+        last_nominal = nominal
+
+def implmement_sockinfo(nominal):
+    (actual, tdonor, there) = fdmap[nominal]
     # socket.fromfd requires the AF.  But of course we don't know the AF.
     # There isn't a sane way to get it in Python:
     #  https://utcc.utoronto.ca/~cks/space/blog/python/SocketFromFdMistake
@@ -61,7 +62,7 @@ def implmement_sockinfo(here):
         print $family, "\n" or die $!;
     '''
     famp = subprocess.Popen(
-        stdin = fd,
+        stdin = actual,
         stdout = subprocess.PIPE,
         args = ['perl','-we',perl_script]
     )
@@ -82,17 +83,36 @@ def implmement_sockinfo(here):
     sock.close()
 
 def permute_fds_for_exec():
-    actual_map = { info[0]: intent for intent, info in fdmap.items }
-    for intent, (actual, tdonor, intarget) in fdmap.items():
-        if intent is not None:
-            in_way = actual_map.get(intent)
-            if in_way is not None:
-                moved = os.dup(intent)
-                actual_map[moved] = 
+    actual2intended = { info[0]: nominal for nominal, info in fdmap.items }
+    # invariant at the start of each loop iteration:
+    #     for each intended (aka `nominal') we have processed:
+    #         relevant open-file is only held in fd intended
+    #         (unless `nominal' is None in which case it is closed)
+    #     for each intended (aka `nominal') we have NOT processed:
+    #         relevant open-file is only held in actual
+    #         where  actual = fdmap[nominal][0]
+    #         and where  actual2intended[actual] = nominal
+    # we can rely on processing each intended only once,
+    #  since they're hash keys
+    # the post-condition is not really a valid state (fdmap
+    #  is nonsense) but we call this function just before exec
+    for intended, (actual, tdonor, there) in fdmap.items():
+        if intended == actual:
+            continue
+        if intended is not None:
+            inway_intended = actual2intended.get(intended)
+            if inway_intended is not None:
+                inway_moved = os.dup(intended)
+                actual2intended[inway_moved] = inway_intended
+                fdmap[inway_intented][0] = inway_moved
+            os.dup2(actual, intended)
+        os.close(actual)
 
 def implement_exec(argl):
     if donor is not None: donor.detach()
-    
+    sys.stdout.flush()
+    permut_fds_for_exec()
+    os.execvp(argl[0], argl)
 
 def set_donor(pid):
     global donor
@@ -117,7 +137,6 @@ def process_args():
                   callback='ocb_set_donor')
 
     args = sys.argv
-    pending = []
 
     while True:
         (ov, args) = op.parse_args(args=args, values=ov)
@@ -128,20 +147,20 @@ def process_args():
         if donor is not None:
             set_donor(int(arg))
         elif arg_matches(r'^(?:(\d+)=)?(\d+)?$'):
-            (here, there) = m.groups()
-            here = None if here is None else int(here)
+            (nominal, there) = m.groups()
+            nominal = None if nominal is None else int(nominal)
             there = int(there)
-            pending.append = (here,there)
+            pending.append = (nominal,there)
         elif arg = 'exec':
             if not len(args):
                 op.error("exec needs command to run")
             implement_pending()
             implement_exec(args)
         elif arg = 'sockinfo':
-            if last_here is None:
+            if last_nominal is None:
                 op.error('sockinfo needs a prior fd spec')
             implement_pending()
-            implement_sockinfo(last_here)
+            implement_sockinfo(last_nominal)
         else:
             op.error("unknown argument/option `%s'" % arg)
 
@@ -149,9 +168,9 @@ def process_args():
     
 
             there = int(m.group[1])
-            here = None if m.group
+            nominal = None if m.group
 
-            ,here) = map(int, m.groups())
+            ,nominal) = map(int, m.groups())
             
 
 pid = int(sys.argv[1])